1. Field of the Invention
The present invention relates to a discharge vessel or chamber for a high-intensity discharge lamp and particularly, to a discharge vessel or chamber having a capillary at each end thereof for holding an electrode and a method of fabricating the same.
2. Description of Related Art
Ceramic discharge vessels or chambers for high-intensity discharge lamps are generally classified as either an integral type where the central body defining a discharge space and a capillary for holding an electrode are integrally formed with each other, or an assembly type, wherein the body and the capillary are separately fabricated as two different components and assembled together. In either type, as shown in the explanatory cross sectional view of FIG. 6, an electrode fabricated by an electrode material 12 with a discharge electrode 14 made of tungsten or the like joining to the distal end of a current conductor 13 made of niobium, molybdenum, or the like inserted into capillary 11 made of an alumina based ceramic material or an alumina material before the gap between the electrode and the capillary is sealed air-tightly with a frit sealer 15 made of a glass material.
The discharge vessel or chamber is then baked at its body and capillary simultaneously at a proper temperature.
As the discharge vessel or chamber of such a conventional capillary type is baked at a high temperature for increasing the permeability of light across its body, the physical strength tends to decline. In particular, when the capillary is joined and sealed with the electrode, it may possibly crack. It is hence essential for preventing any cracks to control the frit sealer to a precise amount and increase the thickness or physical strength of the capillary.
However, controlling the amount of the frit sealer requires a highly precise technique while increasing the thickness of the capillary interrupts the down-sizing of a resultant discharge lamp.
It is thus an object of the present invention, in view of the above aspects, to provide a discharge vessel or chamber for a high-intensity discharge lamp capable of inhibiting crack generation without controlling the frit sealer to a precise amount or increasing the thickness of the capillary and a method of fabricating the same.